1. Field of the Invention
The invention relates generally to the field of bi-directional power conversion devices. More specifically, the invention is directed towards a bi-directional DC-AC or DC-DC power conversion device.
2. Description of Related Art
Known commercial vehicles, such as a recreational vehicle or a boat, may have multiple DC ports. The DC ports may be battery terminals, and each battery may have different characteristics and charging needs. In particular, such batteries may be maintained at different voltages. Further, power may be transferred between batteries having different voltages and between the batteries and an AC port, such as an AC generator. Devices exist for transferring power between a plurality of DC ports of the same or different voltages and between DC and AC ports. However, such known devices are often inefficient. In these known devices, current flowing through each DC port may not be entirely or even substantially DC, which decreases power transfer efficiency.
For example, a known conversion device may convert directly between a first DC port voltage and a second voltage, where the second voltage may be at least four times the first DC port voltage, and may between thirteen and sixteen times the first voltage. A direct conversion between the first DC port voltage and the second voltage may decrease efficiency of power transfer. Further, a known conversion device may comprise a transformer. In such a device, a turns ratio between a secondary side of the transformer and a primary side of the transformer may be equal to a ratio between the second voltage and the first DC port voltage. Therefore, a direct conversion between the first DC port voltage and the second voltage also may increase transformer leakage inductance by providing a turns ratio between the secondary side and the primary side of greater than four.
Further, it has become increasingly useful to utilize hydrogen fuel cells as DC ports. However, hydrogen fuel cells often may change their voltages inefficiently in response to a change in a voltage measured at a load. Moreover, the known devices for transferring power between a plurality of DC ports of the same or different voltages and between DC and AC ports may not efficiently compensate for the hydrogen fuel cell""s often inefficient response to changes in the voltage measured at the load.
Therefore a need has arisen for an apparatus that overcomes these and other shortcomings of the related art. An object of the present invention is that a bi-directional power converter for transferring power between a plurality of power supply ports is provided. Another technical advantage of the present invention is that the bi-directional power converter may transfer power in either direction between any combination of the power supply ports and a plurality of AC ports. Still another technical advantage of the present invention is that the bi-directional power converter may transfer power in either direction when the plurality of power supply ports each have different voltages. Still yet another technical advantage of the present invention is that the bi-directional power converter may provide a substantially or entirely DC current flowing through the power supply ports.
According to an embodiment of the present invention, a bi-directional power converter is described. The converter comprises a first bi-directional DC-DC conversion device having a first plurality of bi-directional DC-DC converters. It further may comprise a plurality of power supply ports, each connected to at least one of the first plurality of bi-directional DC-DC converters and a voltage medium capacitor. The power supply ports transfer power to each other. The voltage medium capacitor is connected to each of the first plurality of bi-directional DC-DC converters and has a first capacitor voltage greater than a second voltage measured at each of the power supply ports.
In another embodiment of the present invention, a bi-directional power converter is described. The converter comprises a first bi-directional DC-DC conversion device having a first plurality of bi-directional DC-DC converters. It further may comprise a plurality of power supply ports, each connected to at least one of the first plurality of bi-directional DC-DC converters, which power supply ports transfer power to each other, and a voltage medium capacitor, which is connected to each of the first plurality of bi-directional DC-DC converters and has a first capacitor voltage greater than a second voltage measured at each of the power supply ports. In addition, the converter comprises at least one second bi-directional DC-DC conversion device having a second plurality of bi-directional DC-DC converters. Moreover, the first bi-directional DC-DC conversion device and each of the second bi-directional DC-DC conversion devices are connected in parallel. Further, the converter comprises a third bi-directional DC-DC converter device, which is connected to the voltage medium capacitor and a voltage high capacitor, and a bi-directional AC-DC conversion device, which is connected to the voltage high capacitor and at least one inductor, which is connected to a plurality of AC ports.
Other objects, features, and advantages will be apparent to persons of ordinary skill in the art in view of the following detailed description of the invention and the accompanying drawings.